Optimization of plasma-enhanced chemical vapor deposition silicon oxynitride layers for integrated optics applications

Silicon oxynitride (SiOxNy:H) layers were grown from 2%SiH4/N2 and N2O gas mixtures by plasma-enhanced chemical vapor deposition (PECVD). Layer properties such as refractive index, deposition rate, thickness non-uniformity and hydrogen bond content were correlated to the relevant deposition parameters including radio frequency power, chamber pressure, total gas flow, substrate temperature and N2O/SiH4 gas flow ratio. As a result, optimized SiOxNy:H layers could be produced over a wide index range (1.46–1.70) with good thickness uniformity and sufficiently high deposition rate. With a refraction index non-uniformity < 5 × 10− 4 a thickness non-uniformity could be obtained below 1% over a 70 × 70 mm2 area of a 100 mm wafer at a deposition rate > 50 nm/min. The material composition and the optical properties of the SiOxNy:H layers were characterized by spectroscopic ellipsometry, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared spectroscopy and prism coupler techniques. A simple atomic valence model is found to describe the measured atomic concentrations for PECVD silicon oxynitride layers.